1. Field of the Invention
This invention relates generally to a regulator spool valve controlled by a direct acting solenoid located in a machined main control casting of an automatic transmission.
2. Description of the Prior Art
An automatic transmission includes a hydraulic system for regulating fluid pressure and hydraulic fluid flow in various lines connected to components of the transmission. The system includes a regulator spool valve packaged in a main control casting, which is machined at a transmission production plant. The casting, preferably of an aluminum alloy, is usually referred to as a valve body. The components of the system are assembled in the valve body and have transfer functions characterized at the plant.
A solenoid-actuated shift valve controls pressure communicated from the valve to a clutch or brake whose state of engagement and disengagement determines the gear in which the transmission operates. But the dimensional tolerance stack-up in most valve body castings is too large to permit use of a practical integrated electromagnet and achieve required flow and pressure regulation accuracy.
A need exists in the industry for a regulator spool valve formed in a valve body and having an electric solenoid directly integrated into the valve such that the dimensional tolerances are not an obstacle to accuracy of pressure regulation and fluid flow.